Numerous studies have shown acute alterations in left ventricular function and morphology after cardiopulmonary bypass (CPB), but long-term changes occurring in chronic survivors have not been documented. This study assesses the long-term effects of CPB in combination with popular methods of myocardial protection. Thirty-seven dogs were placed on CPB for 100 minutes using a bubble oxygenator without hemodilution, maintaining mean aortic pressure at 80 mm. Hg. The left ventricle was vented. The animals were divided into three groups: 1. Normothermic anoxic arrest for 60 minutes (aortic occlusion). 2. Continuous coronary perfusion with an empty, beating heart for 60 min. at 35 degrees C. 3. Hypothermic anoxic arrest (aortic occlusion) for 60 min. with topical cold saline lavage (4 degrees C).